The design of aircraft is highly dependent on the dynamics of fluid flow around the aircraft. For nearly 100 years, the field of aerodynamics has recognized that the flow in a thin boundary layer on the surface is critical to the efficient design of an aircraft. The flow in the boundary layer is initially smooth (i.e., laminar), but at some point transitions to a turbulent flow. Transition to turbulent flow in flight is due to many factors, including surface condition and acoustical noise. Turbulent flow is undesirable since it brings about increased drag and heat transfer to the aircraft. Thus, systems and methods to delay the laminar-to-turbulent flow transition are a major objective of aerodynamic research.
Decades of research in aerodynamics have shown little progress in delaying a boundary layer's transition to a turbulent condition. Early attempts to modify the boundary layer characteristics have included very thin modifications of the surface such as the addition of sandpaper, tape, or flapping layers. More recent and sophisticated attempts include the addition of small isolated protrusions (or “trips” as they are known) near the leading edge of an aircraft's wing span. Prior efforts have emphasized the separation of the trips or alignment of the trips along the stream-wise direction of the flow in which case the trips are referred to as “riblets”. Unfortunately, to date, trip-based modification of a boundary layer flow has only achieved modest amounts of success.